Pain of the joints of the body is a common problem. One of the most important joint which is liable to wearing and disease is the knee. The knee provides support and mobility and is the largest and strongest joint in the body. Pain in the knee may be caused by for example injury, arthritis or infection. The weight-bearing and articulating surfaces of the knees, and of other joints, are covered with a layer of soft tissue that typically comprises a significant amount of hyaline cartilage. The friction between the cartilage and the surrounding parts of the joint is very low, which facilitates movement of the joints under high pressure. The cartilage is however prone to damage due to disease, injury or chronic wear. Moreover it does not readily heal after damage, as opposed to other connective tissue, and if healed the durable hyaline cartilage is often replaced by less durable fibro cartilage. This means that damage to the cartilage gradually becomes worse. Along with injury or disease comes the problem with pain, which results in handicap and loss of function. It is therefore important to have efficient means and methods for repairing damaged cartilage in joints, for example in knee joints.